The next drop likely won't happen until the currently fulfilling drop ships. The drop hasn't shipped yet and won't be shipping until the end of May. We're supposed to get an update soon so just keep an eye on the latest comments from Massdrop for how long it takes to ship. After fulfillment and shipping finishes for the last drop, they'll likely consider another drop.

Heck, if I can get the other Summoner designs I'd be in on another drop. ;)